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The phylogenetic position of Vibrio iliopiscarius was inferred by the maximum-likelihood, maximum-parsimony and neighbour-joining methods on the basis of almost complete 16S rRNA gene sequences. The results showed that this species falls into the same cluster as Photobacterium species and is clearly distinct from other Vibrio species. Its nearest phylogenetic neighbour is Photobacterium phosphoreum. From these results, it is concluded that V. iliopiscarius should be reclassified as Photobacterium iliopiscarium comb. nov., the type strain of which is PS1T (= ATCC 51760T).

The phylogenetic relationships of 50 reference strains, mostly marine bacteria which require Na+ for growth, were determined on the basis of 600 16S rRNA nucleotides by using reverse transcriptase sequencing. Strains belonging to 10 genera were included (four genera of the family Vibrionaceae, the genus Aeromonas of the family Aeromonadaceae, and the genera Alteromonas, Marinomonas, Shewanella, Pseudomonas, and Deleya). The sequences were aligned, the similarity values and evolutionary distance values were determined, and a phylogenetic tree was constructed by using the neighbor-joining method. On the basis of our results, the family Vibrionaceae was separated into at least seven groups (genera and families). Vibrio marinus clearly was on a line of descent that was remote from other vibrios. As determined by the similarity and evolutionary distance values, V. marinus is more distantly related to the family Vibrionaceae than the members of the Aeromonadaceae are. Also, Vibrio cholerae strains formed a separate group with Vibrio mimicus at the genus level. Of 30 species of the Vibrionaceae, 17 formed a large phylogenetic cluster. The genus Listonella was found to be a heterogeneous group, and the species were distributed in various subgroups of the Vibrionaceae. The separation of the family Aeromonadaceae from the family Vibrionaceae and the separation of the genera Marinomonas and Shewanella from the genus Alteromonas were confirmed in this phylogenetic study. However, a marine Pseudomonas species, Pseudomonas nautica, was clearly separated from two terrestrial Pseudomonas species. Each group that was separated by the phylogenetic analysis had characteristic 16S rRNA sequence patterns that were common only to species in that group. Therefore, the characteristic sequences described in this paper may be useful for identification purposes.

Four strains of tetrodotoxin-producing bacteria isolated from a red alga and from pufferfish were characterized. Two of these strains are members of the genus Listonella MacDonell and Colwell. The phenotypic characteristics, guanine-plus-cytosine contents, and base sequences of the 16S rRNAs of these organisms indicated that they are members of Listonella pelagia (Vibrio pelagius) biovar II. The other two strains are members of the genus Alteromonas Baumann et al. and the genus Shewanella MacDonell and Colwell. These two strains are mutually distinct and distinct from the previously described Alteromonas and Shewanella species and therefore are placed in new species. The names Shewanella alga and Alteromonas tetraodonis are proposed for these organisms; the type strains are strains OK-1 and GFC, respectively.